The simplest form of a carbohydrate is a single-sugar molecule (glucose, fructose or galactose).
Glucose is the most common form of sugar and is a major source of fuel for the cells in the human body.
Sucrose is also known as common table sugar and is made up of glucose and fructose.
Lactose is the sugar found in milk and is made up of glucose and galactose.
Fructose is the sugar found in fruit.
There are many others too – for example, dextrin, maltose and maltodextrins!
All sugars are not the same. Many foods naturally high in sugars are very nutritious like fruit, milk and yoghurt. Unfortunately food labels don’t help you distinguish between the slowly absorbed and the rapidly absorbed sugars or tell you whether the sugars are naturally occurring or added.
What are starches?
Starches are long chains of the sugar glucose joined together.
Starches (formerly known as complex carbohydrates) occur naturally in a large range of foods including nutrient-rich foods like root vegetables, legumes, cracked wheat, brown rice, pearl barley, quinoa and oats. Starch is also found in refined products such as cornflour, white bread, many breakfast cereals, potato crisps, French fries, rice crackers/cakes, biscuits, cakes, and pastries.
Refined starches are invisible, they are not listed in the Nutrition Information\Nutrition Facts Panel on foods, and the names for added refined starches are often unpronounceable like acetylated distarch phosphate, or food additive code number 1414.
Starches are generally not sweet tasting. There are two types of starch in food; amylose and amylopectin. The ratio of the two starches has an effect on the GI value in some foods.
So why are they not good for our health? Refined starches contain essentially the same amount of Calories (kJs), total carbohydrate and fibre as refined sugars, and unless fortified, are just as devoid of vitamins and minerals. They also have a high GI. In a nutshell, refined starches are as detrimental to our health as refined sugars.
When choosing foods for a healthy diet, you should avoid foods containing highly refined starches (e.g. white bread) as well as highly refined sugars (e.g. table sugar).
Fibre is a form of indigestible carbohydrate found in mainly in plant foods, or what your grandmother called ‘roughage’. It comes in two forms:
Insoluble Fibre, the kind mostly found in vegetables, wheat, wholegrains as well as nuts and seeds. They help with ‘laxation’, keeping your bowels moving and regular.
Soluble Fibre: a gummy substance that is a component of dried peas, beans, oats, barley and fruits. They may help reduce blood cholesterol re-absorption and keep blood glucose levels.
Fibre slows the digestion of food, so glucose is released into the blood stream more gradually, helping you feel fuller. Soluble fibre in particular appears to improve blood glucose and insulin sensitivity. Perhaps more significant is that a number of studies in the general population have linked eating fibre with a lower risk of heart disease.
|Children & Adolescents||Age||Adequate Intake|
|All||1-3 yr||14 g/day|
|4-8 yr||18 g/day|
|Boys||9-13 yr||24 g/day|
|14-18 yr||28 g/day|
|Girls||9-13 yr||20 g/day|
|14-18 yr||22 g/day|
|Men||19-70 yr||30 g/day|
|>70 yr||30 g/day|
|Women||19-30 yr||25 g/day|
|>70 yr||25 g/day|
|Pregnancy||14-18 yr||25 g/day|
|19-50 yr||28 g/day|
|Lactation||14-18 yr||27 g/day|
|19-30 yr||30 g/day|
Source: Adapted from National Health & Medical Research Council – Nutrient Reference Values for Australia & New Zealand
Resistant Starch is another type of dietary fibre. It’s actually a starch that ‘resists’ digestion and absorption in the small intestine and travels through the large intestine largely intact. It ends up in the small intestine where it is fermented into short chain fatty acids by good bacteria. There is strong evidence that resistant starch may be important in reducing the risk of bowel cancer. It is found mostly in beans, lentils, unripe bananas as well as unprocessed cereals and wholegrains. Resistant starch is also created from cooling down cooked rice, pasta and potatoes.